$144 Cheap United flights St. Louis (STL) to Cancun (CUN)

Apply the "Price (lowest to highest)" filter on Expedia to search for cheap United Airlines round-trip flights from $308 from STL to CUN. Affordable one-way fares from $144 are also on offer.**These prices were available on Expedia within the past 7 days, for flights departing within the next year. Prices and availability are subject to change. Additional terms apply.

Snagging the best United Airlines deals from STL to CUN is typically all about timing. You can save 17% on international flights when you book 18 to 29 days before takeoff instead of four to five months ahead. As an added bonus, you can pocket 17% on average by buying your tickets on a Sunday compared to a Friday, which is usually the most expensive day to book.* It's a good idea to start searching for flights about one month before you want to travel.*Ideal booking window recommendation is based on average round-trip ticket prices for January through November for 2024. Best day of the week to book recommendation is based on average round-trip ticket prices for January through October 2024. All data sourced from ARC's global airline sales database.

To find the earliest departures from STL to CUN with United Airlines, filter your search by "Early Morning" and "Morning." Booking an early flight generally means you're less likely to experience cancellations.**Most reliable time of the day recommendation is based on January through August 2024 flight status data sourced from OAG's global flight data platform.

A rewarding loyalty program and the opportunity to collect points through United Mileage Plus are the start of the reasons to depart from STL to CUN with United Airlines. Plus, when you join our One Key™ program, you can receive OneKeyCash™* in addition to any airline loyalty program earnings. It's yours to use wherever your next trip takes you.*OneKeyCash™ disclaimer - OneKeyCash™ is not redeemable for cash and can only be used on Expedia, Hotels.com and Vrbo.